1. Field of the Invention
The present invention is related to a circuit for generating a direct current voltage and method thereof, and particularly to a circuit for generating a direct current voltage and method thereof that can utilize a limiting direct current voltage generator to limit the direct current voltage.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a diagram illustrating an electromagnetic coupling charging circuit 100 according to the prior art. The electromagnetic coupling charging circuit 100 includes an inductor 102, an antenna capacitor 104, a diode 106, and a charging capacitor 108, where the antenna capacitor 104 is used for adjusting a resonant frequency between the antenna capacitor 104 and the inductor 102 to match a frequency of an electric wave RW transmitted by a reader 110, and the inductor 102 is used for coupling the electric wave RW transmitted by the reader 110. When an electric wave coupled by the inductor 102 provides a forward bias for the diode 106, the electric wave coupled by the inductor 102 can charge the charging capacitor 108.
However, charging efficiency of the electromagnetic coupling charging circuit 100 is poor due to an influence of a voltage drop of the diode 106. In addition, an amplitude of the electric wave coupled by the inductor 102 varies with a distance between the electromagnetic coupling charging circuit 100 and the reader 110, so a voltage of node A may damage another circuit 112.